Generally, in order to manufacture a semiconductor integrated circuit, various thermal processes such as a film forming process, an annealing process, an oxidation and diffusion process, a sputtering process, an etching process and the like are repeatedly performed several times repeatedly on a semiconductor wafer.
The factors for improving uniformity of a film quality, a film thickness and the like on the semiconductor wafer include uniformity of distribution or flow of a reactant gas, uniformity of a wafer temperature, uniformity of a plasma and the like.
In order to obtain such uniformity in the circumferential direction of the wafer, it is required to rotate the wafer. A conventional wafer rotating mechanism includes a disc-shaped member for supporting a wafer; and a driving mechanism for rotating the disc-shaped member by frictional force generated by contact between the driving mechanism and the disc-shaped member.
Since, however, friction between objects generates particles, it is inevitable that particles are generated from contact/friction portions in the conventional wafer rotating mechanism. Further, misalignment due to sliding occurs between the disc-shaped member for supporting the wafer and a rotation unit of the driving mechanism for the disc-shaped member, so that a returning operation to a reference position is required each time. This causes deterioration of a throughput.
In view of the above, U.S. Pat. No. 6,157,106 (hereinafter, referred to as “Patent Document 1”) discloses a configuration in which a rotor for supporting a wafer is rotated while being magnetically floated so that particles are not generated in a processing chamber. In the technique disclosed in Patent Document 1, the rotor is a constituent element for floating a rotor system by magnetic force. Moreover, a magnetic field is generated by a stator assembly including a permanent magnet for floating and an electromagnet for control.
In the technique described in Patent Document 1, although the rotor is floated by magnetic force applied thereto in a horizontal direction, the direction of the magnetic force does not coincide with the vertical direction of gravity applied to the rotor, so that vector directions of acting force are dispersed. As a result, it is complicated and difficult to control the magnetic floating.